An ignition plug may be used to ignite a fuel-air mixture in a cylinder of a direct-injection, applied ignition internal combustion engine. The ignition plug may include at least one electrode pair with two electrodes which are electrically insulated and spaced apart from one another. The first electrode may serve as the ground. The spacing between the first and second electrodes is the ignition gap in which the spark path forms during the course of applied ignition.
One approach to adjust ignition performance is to employ an ignition plug with variable electrode spacing as a function of the present operating temperature of the internal combustion engine. In one example, the ignition plug has relatively small electrode spacing at low temperatures and increases the spacing as temperature increases to higher values. Another example has the electrode spacing initially increasing with increasing temperature during the warm-up phase and then decreasing the electrode spacing with further increasing engine operating temperatures beyond a predefined threshold temperature. Both approaches use a bimetallic element having two components with different thermal expansion properties.
Some of the problems recognized by the inventors with the previous ignition plug with variable electrode spacing as a function of the present engine operating temperature come from increasing the spacing as temperature increases or to a predefined threshold temperature. An ignition plug of said type has a relatively small spacing during the warm-up phase in both approaches, which can degrade reliable ignition of the fuel-air mixture during the warm-up phase. Further, the inventors have recognized that a large gap at part load operation and a small gap at high load operation better enables reliable ignition of the fuel-air mixture during selected conditions.
In one example the problems described herein may be at least partly addressed by an ignition plug comprises two electrodes which are electrically insulated with respect to and spaced apart from one another. Further the first electrode serves as the ground electrode and the spacing between the first electrode and second electrode may be adjusted for various engine operating parameters using an adjustment device. The first electrode, second electrode, or both the first and second electrode may be movable. This may better enable control over the ignition gap spacing.
In another example, a method for control of a spacing between a first electrode and a second electrode of an ignition plug by means of an adjustment control device as a function of at least one operating parameter of an internal combustion engine wherein an ignition gap spacing can be set variably during engine operation, wherein the method further comprises at least one or more engine operating parameters that may be measured and/or estimated to better enable ignition of a fuel-air mixture. This may provide reliable ignition of the fuel-air mixture over a variety of engine operating conditions.